It is common for internal combustion engines to be associated with a cooling system, to dissipate heat from the engine in order to prevent engine damage through overheating. Such cooling systems usually employ fluid coolants due to their thermal conductivity, and their ability to circulate throughout the cooling system.
A typical basic cooling system, such as for the engine of a motor vehicle, comprises a fluid coolant such as water, and in some cases additives which modify the freezing and boiling point of the coolant, a coolant reservoir such as a radiator or header tank with a removable cap and overflow outlet, a pump to assist circulation of the coolant, and a series of fluid conduits for circulation of fluid from radiator to an engine block, from the engine block to a heater, from the heater back to the engine block, and from the engine block back to the radiator. The coolant fluid removes heat from the engine, and is then cooled by being passed through the radiator, which comprises a relatively large surface area exposed to cool air such as supplied by a fan, or by air forced past the radiator through movement of the vehicle. However, if leaks in the cooling system are present, such leaks would lead to substantial loss of cooling fluid and will also make the cooling system work inefficiently, with the result that the engine can overheat. Although devices such as a temperature gauge can indicate overheating before damage occurs to the engine, detecting the source of the leak with a view to repair is often difficult, time consuming and expensive. Diagnosis of leaks is often complicated by the fact that the rate of fluid loss can be very slow, and therefore difficult to detect by observation.
Several types of pressure testing apparatus are available that aid in the detection of cooling system leaks. A standard conventional type comprises a cap-like fixture associated with a hand pump having a non-return valve and a pressure gauge in fluid communication with the hand pump, the cap-like fixture being attachable to an inlet of a radiator, after the radiator cap has been removed. The cap-like fixture did not incorporate any pressure relief valve as is common with conventional radiator caps. In this conventional pressure testing apparatus, the hand pump was used to increase the pressure of the cooling system to a desired level as indicated by the pressure gauge, after which a fall in pressure was indicative of a leak somewhere in the cooling system or the non-return valve of the hand pump. In a variation of this arrangement, an inflatable bladder was used in substitution of the cap-like fixture which is described in U.S. Pat. No. 5,557,966.
In relation to the aforementioned prior art, a number of disadvantages are applicable which are set out hereunder:
(a) the engine must be turned off to avoid loss of coolant when the radiator cap is removed with the result that the cooling system is not tested under normal operating temperature conditions; PA1 (b) the integrity of the radiator cap and its seal with the radiator inlet cannot be tested simultaneously with operation of the pressure testing apparatus; PA1 (c) the pressure testing apparatus is labour intensive, requiring frequent hand pumping to repeatedly pressurize the cooling system should it be difficult to find a leak; and PA1 (d) accidental over-pressurization can damage components of the cooling system and the engine, as the radiator cap, which is removed during operation of the device, provides the only means of relieving pressure in the cooling system. PA1 a first air conduit; PA1 means for regulating air pressure associated with said first air conduit to maintain air pressure at a predetermined value; and PA1 means for switching off the flow of pressurized air from the source, whereby, in use, pressurized air can be supplied to the cooling system via the first air conduit to initially pressurize the cooling system and subsequent detection of any fluid leaks present takes place when said flow of pressurized air is switched off and said air pressure maintained at said predetermined value. PA1 (i) placing the cooling system in fluid communication with a source of pressurized air; PA1 (ii) passing pressurized air into the cooling system; PA1 (iii) adjusting the pressure developed within the cooling system to a predetermined value which may accord with manufacturers' specifications which is usually less than a maximum pressure rating of the cooling system; PA1 (iv) if desired, switching off the source of pressurized air; PA1 (v) checking for pressure leaks within said cooling system; and PA1 (vi) allowing for exhausting of coolant from the cooling system by directing the flow of coolant into a receptacle from an exhaust conduit.
Reference may also be made to U.S. Pat. No. 4,449,402 which refers to a pressure testing apparatus which comprises a conduit, a source of pressure for the conduit, a pressure gauge for determining the level of pressure within the conduit, a check valve interposed between the pressure source and the conduit, and means for connection of the conduit to a vent of a filler neck of a radiator which filler neck is engageable with a radiator cap. The filler neck has an open mouth surrounded by an outer seat and there is also provided an inner seat as well as an overflow vent and an interior chamber between the inner and outer seats. The radiator cap engages with the inner seat of the filler neck to form outer and inner seals. The radiator cap also includes a vacuum valve operative as a bypass of pressure from the interior chamber of the filler neck through the radiator cap into the engine cooling system. The pressure testing apparatus of U.S. Pat. No. 4,449,402 therefore allows the integrity of the radiator and cap seals and the cooling system to be tested simultaneously while retaining the relief valve function of the radiator cap.
However, the pressure testing apparatus of U.S. Pat. No. 4,449,402 was subject to the aforementioned disadvantages (a), (c) and (d).
However, while disadvantage (b) was not directly applicable, it was the case that the pressure testing apparatus of U.S. Pat. No. 4,449,402 could not efficiently detect any leaks in the radiator cap in an efficient manner because of a multiple step procedure being required for initial pressurization of the cooling system to attain the appropriate maximum pressure rating followed by decrease of pressure to ambient pressure by control of the check valve. If there is no increase in pressure which would indicate a failure of the inner seal, then it was necessary to remove the cap from the filler neck for separate testing of both seals.
It will also be apparent that disadvantage (d) was clearly applicable in that the pressure testing apparatus of U.S. Pat. No. 4,449,402 can also only test for leaks in the radiator cap when the valve stem in the vacuum relief valve is in the open position. This also means that when the pressure testing apparatus is operational, the vacuum relief valve is inoperative and thus there is no inbuilt pressure relief valve to detect over-pressurization of the cooling system which can cause rupture or damage to the cooling system.
It was also necessary to appreciate that the pressure testing apparatus of U.S. Pat. No. 4,449,402 has a very limited application in that it can only be applied to a radiator cap having inner and outer seals as described above. Therefore, it can only be applied to a limited number of internal combustion cooling systems.
Reference may also be made to U.S. Pat. No. 5,105,653 which refers to pressure testing apparatus, a valve assembly housing which includes a valve inlet connectable to a source of compressed air, a metering orifice adjacent to the inlet in fluid communication with internal passages of the housing for transmission of compressed air, a check valve which maintains compressed air in the internal passages of the housing and which also may communicate with low pressure passages in the housing which lead to an air pressure gauge, a pressure relief valve communicating with the low pressure passages, a low pressure outlet passage connectable to a flexible hose which is attached to a radiator test adaptor which connects the hose to the filler neck of a standard radiator to discharge low pressure air into the cooling system of a vehicle as well as a secondary pressure relief valve holding a seal at the mouth of the filler neck.
However, it is clear in relation to the pressure testing apparatus of U.S. Pat. No. 5,105,653 that the abovementioned disadvantages (a) and (b) referred to above is applicable. However, it was also relevant to note that this pressure testing apparatus was unduly complicated in structure which necessitates provision of relevant tooling for manufacture of the valve assembly housing. Two pressure relief valves are required. The adaptor is of specialized structure and adapted to replace the standard radiator cap in use. The pressure testing apparatus is only attachable at the radiator filler neck and thus is of limited application.
Another method of pressurizing the cooling system is described in U.S. Pat. No. 4,458,523, wherein water is introduced into the fluid conduit connecting the heater and engine block to achieve a desired pressure and so allow visual and auditory detection of fluid leaks in the cooling system, and the integrity of the seal between radiator inlet and cap.
Australian Patent Application 27245/95 also discloses a pressure testing apparatus that introduces water heated to a temperature similar to that achieved under engine running conditions directly into the engine block. Thus, leaks which appear during normal operation, but disappear due to contraction upon cooling, would be more likely to be detected because normal operating temperatures have been achieved.
However, the use of introducing water into the coolant circuit requires ancillary apparatus not required for systems using pressurized or compressed air and is labour intensive.
Reference may also be made to a conventional pressure testing apparatus marketed under the trade mark "FLO-KLEEN" which is available from Flo-Kleen Products of Balcatta, Western Australia. In one arrangement, the pressure testing apparatus included an air conduit which was attachable to a bleed hose or overflow hose of a radiator by an adaptor incorporating a manually operable lock-on handle. The air conduit was attachable to a hand pump incorporating a pressure dial for measuring the pressure when required. However, this pressure testing apparatus did not include a regulator and hence could not be connected to an air compressor. There was also no means for exhausting or venting coolant from the cooling system being tested from the FLO-KLEEN apparatus after use. Again, this mitigated against connection of the FLO-KLEEN apparatus to a compressor.
In an alternative arrangement, the FLO-KLEEN pressure testing apparatus included an air conduit which could permanently replace the coolant drain plug in the side of the engine block. This alternative arrangement also included a trigger operated device attached to the air conduit wherein the trigger operated device also included a pressure dial for measurement of the pressure in use. This arrangement could be connected to an air compressor and associated regulator and, to this end, there was also provided a pressure release mechanism which was a spring operated button or projection which, when pressed inwardly against the bias of the spring, could also release excess fluid in the cooling system and pressure testing apparatus to atmosphere. However, this pressure testing apparatus did not include any means for switching off the flow of pressurized air from the compressor and thus the compressor could not be utilized for other purposes if desired.
Another disadvantage of this alternative arrangement was that the compressor could not be disconnected from the cooling system in use.